Incorporation of Particulate Additives Into Metal Working Surfaces

ABSTRACT

A mechanical device and method for lapping a metal working surface, the device including: (a) a workpiece having the metal working surface; (b) a contact surface, disposed generally opposite the working surface, for moving in a relative motion to the working surface; (c) a plurality of abrasive particles, disposed between the contact surface and the working surface, and (d) a mechanism, associated with at least one of the surfaces, for applying the relative motion, and for exerting a load on the contact surface and the working surface, the contact surface for providing an at least partially elastic interaction with the abrasive particles, wherein, associated with the contact surface is a particulate additive material, and wherein, upon activation of the mechanism, the relative motion under the load causes a portion of the abrasive particles to lap the working surface, and wherein the relative motion under the load effects incorporation of a portion of the particulate additive material into the working surface.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to metal working surfaces having particulate additive materials such as solid lubricants, and to devices and methods for incorporating such materials into the metal working surfaces.

In order to reduce friction and wear in mechanically interacting surfaces, a lubricant is introduced to the zone of interaction. As depicted schematically in FIG. 1A, opposing surfaces 32 and 34 move at a relative velocity V. Under ideal lubricating conditions, a lubricant film 20 between these surfaces forms an intact layer that permits the moving surfaces to interact with the lubricant. Under such conditions, no contact between surfaces 32 and 34 occurs at all, and the lubricant layer is said to carry a load P that exists between the opposing surfaces. If the supply of lubricant is insufficient, a reduction in the effectivity of the lubrication ensues, which allows surface-to-surface interactions to occur.

As shown schematically in FIG. 1B, below a certain level of lubricant supply, the distance between opposing, relatively moving surfaces 32 and 34 diminishes because of load P, such that surface asperities, i.e., peaks of surface material protruding from the surfaces, may interact. Thus, for example, an asperity 36 of surface 34 can physically contact and interact with an asperity 38 of surface 32. In an extreme condition, the asperities of surfaces 32 and 34 carry all of the load existing between the interacting surfaces. In this condition, often referred to as boundary lubrication, the lubricant is ineffective and the friction and wear are high.

Grinding and lapping are conventional methods of improving surface roughness and for producing working surfaces for, inter alia, various tribological applications. FIG. 1C (i)-(ii) schematically illustrate a working surface being conditioned in a conventional lapping process. In FIG. 1C(i), a working surface 32 of a workpiece 31 faces a contact surface 35 of lapping tool 34. An abrasive paste containing abrasive particles, of which is illustrated a typical abrasive particle 36, is disposed between working surface 32 and contact surface 35. Contact surface 35 of lapping tool 34 is made of a material having a lower hardness with respect to working surface 32. The composition and size distribution of the abrasive particles are selected so as to readily wear down working surface 32 according to plan, such as reducing surface roughness so as to achieve a pre-determined finish.

A load is exerted in a substantially normal direction to surfaces 32 and 35, causing abrasive particle 36 to penetrate working surface 32 and contact surface 35, and resulting in a pressure P being exerted on a section of abrasive particle 36 that is embedded in working surface 32. The penetration depth of abrasive particle 36 into working surface 32 is designated by h_(a1); the penetration depth of abrasive particle 36 into contact surface 35 is designated by h_(b1). Generally, abrasive particle 36 penetrates into lapping tool 34 to a greater extent than the penetration into workpiece 31, such that h_(b1)>>h_(a1).

In FIG. 1C(ii), workpiece 31 and lapping tool 34 are made to move in a relative velocity V. The pressure P, and relative velocity V of workpiece 31 and lapping tool 34, are of a magnitude such that abrasive particle 36, acting like a knife, gouges out a chip of surface material from workpiece 31.

At low relative velocities, abrasive particle 36 is substantially stationary. Typically, however, and as shown in FIG. 1C(ii), relative velocity V is selected such that a corresponding shear force Q is large. Because the material of lapping tool 34 that is in contact with abrasive particle 36 is substantially unyielding (i.e., of low elasticity) with respect to the particles in the abrasive paste, these particles are usually ground up quite quickly, such that the abrasive paste must be replenished frequently.

In the known art, grinding, lapping, polishing and cutting are carried out on materials such as metals, ceramics, glass, plastic, wood and the like, using bonded abrasives such as grinding wheels, coated abrasives, loose abrasives and abrasive cutting tools. Abrasive particles, the cutting tools of the abrasive process, are naturally occurring or synthetic materials which are generally much harder than the materials which they cut. The most commonly used abrasives in bonded, coated and loose abrasive applications are garnet, alpha alumina, silicon carbide, boron carbide, cubic boron nitride, and diamond. The relative hardness of the materials is provided in Table 1.

The choice of abrasive is normally dictated by economics, by the desired finish, and by the material being abraded. The above-provided list of abrasive materials is in order of increasing hardness, but is also, coincidentally, in order of increasing cost, with garnet being the least expensive abrasive material and diamond the most expensive.

TABLE 1 Knoop Hardness Material Number garnet 1360 alpha-alumina 2100 silicon carbide 2480 boron carbide 2750 cubic boron nitride 4500 diamond (monocrystalline) 7000

Generally, a soft abrasive is selected to abrade a soft material and a hard abrasive to abrade harder types of materials in view of the cost of the various abrasive materials. There are, of course, exceptions such as very gummy materials where the harder materials actually cut more efficiently. Furthermore, the harder the abrasive grain, the more material it will remove per unit volume or weight of abrasive. Super-abrasive materials include diamond and cubic boron nitride, both of which are used in a wide variety of applications.

The known lapping methods and systems have several distinct deficiencies, including:

-   -   The contact surface of the lapping tool is eventually consumed         by the abrasive material, requiring replacement. In some typical         applications, the contact surface of the lapping tool is         replaced after approximately 50 workpieces have been processed.     -   The lapping processing must generally be performed in several         discrete lapping stages, each stage using an abrasive paste         having different physical properties.     -   Sensitivity to the properties of the abrasive paste, including         paste formulation, hardness of the abrasive particles, and         particle size distribution (PSD) of the abrasive particles.     -   Sensitivity to various processing parameters in the lapping         process.

There is therefore a recognized need for, and it would be highly advantageous to have, a lapping system that overcomes the manifest deficiencies of the known lapping technologies. It would be of further advantage to have a lapping system that produces working surfaces having improved tribological properties.

SUMMARY OF THE INVENTION

According to the teachings of the present invention there is provided a mechanical device for lapping a metal working surface, the device including: (a) a workpiece having the metal working surface; (b) a contact surface, disposed generally opposite the working surface, the contact surface for moving in a relative motion to the working surface; (c) a plurality of abrasive particles, the particles disposed between the contact surface and the working surface, and (d) a mechanism, associated with at least one of the working surface and the contact surface, for applying the relative motion, and for exerting a load on the contact surface and the working surface, the contact surface for providing an at least partially elastic interaction with the plurality of abrasive particles, wherein, associated with the contact surface is a particulate additive material, and wherein, upon activation of the mechanism, the relative motion under the load causes a portion of the abrasive particles to lap the working surface, and wherein the relative motion under the load effects incorporation of a portion of the particulate additive material into the metal working surface.

According to another aspect of the present invention there is provided a mechanical device for lapping a metal working surface of a workpiece, the device including: a contact surface, for disposing generally opposite the metal working surface, the contact surface for moving in a relative motion to the working surface, the contact surface including: (a) at least one polymeric material, and (b) particulate matter, dispersed within the polymeric material, the contact surface having a Shore D hardness within a range of 65-90, the contact surface designed and configured such that during the lapping of the metal working surface of the workpiece, the particulate matter is mechanically transferred from the contact surface and incorporated into the metal working surface.

According to yet another aspect of the present invention there is provided a lapping method including the steps of: (a) providing a system including: (i) a metal workpiece having a metal working surface; (ii) a contact surface, disposed generally opposite the working surface, the contact surface for moving in a relative motion to the working surface; (iii) a plurality of abrasive particles, the particles disposed between the contact surface and the working surface, and (iv) a plurality of solid particles, associated with the contact surface; (b) exerting a load in a substantially normal direction to the contact surface and the metal working surface, (c) lapping the workpiece by applying a relative motion between the metal working surface and the contact surface, so as to (i) effect an at least partially elastic interaction between the contact surface and the abrasive particles such that at least a portion of the abrasive particles contact both the working surface and the contact surface, and (ii) incorporate the particulate additive into the metal working surface.

According to further features in the described preferred embodiments, the contact surface has a Shore D hardness within a range of 40-90.

According to still further features in the described preferred embodiments, the Shore D hardness is within a range of 65-85.

According to still further features in the described preferred embodiments, at least a portion of the abrasive particles simultaneously contact both the working surface and the contact surface.

According to still further features in the described preferred embodiments, at least a portion of the abrasive particles penetrate the working surface.

According to still further features in the described preferred embodiments, the particulate additive material includes a solid lubricant.

According to still further features in the described preferred embodiments, the abrasive particles are freely disposed between the contact surface and the working surface.

According to still further features in the described preferred embodiments, the particulate additive material is disposed within the contact surface, such that upon the activation of the mechanism, the relative motion causes at least a portion of the particulate additive material to be mechanically transferred from the contact surface and to effect the incorporation of the particulate additive material into the metal working surface.

According to still further features in the described preferred embodiments, the contact surface includes a polymeric material, and wherein the particulate additive material is intimately dispersed within the polymeric material.

According to still further features in the described preferred embodiments, the polymeric material includes an epoxy material.

According to still further features in the described preferred embodiments, the polymeric material includes a polyurethane.

According to still further features in the described preferred embodiments, the Shore D hardness is within a range of 65-90, and the impact resistance is within a range of 4-12 kJ/m2.

According to still further features in the described preferred embodiments, the Shore D hardness is within a range of 70-80, and the impact resistance is within a range of 5-8 kJ/m2.

According to still further features in the described preferred embodiments, the contact surface is disposed on a lapping tool.

According to still further features in the described preferred embodiments, the abrasive particles include alumina particles.

According to still further features in the described preferred embodiments, the composition of the contact surface includes both an epoxy material and polyurethane, and wherein the Shore D hardness is within a range of 65-90, and the impact resistance is within a range of 4-9 kJ/m2.

According to still further features in the described preferred embodiments, the composition of the contact surface includes an epoxy material and polyurethane in a weight ratio of 25:75 to 90:10.

According to still further features in the described preferred embodiments, the composition of the contact surface includes polyurethane in a range of 3% to 75%, by weight.

According to still further features in the described preferred embodiments, the composition of the contact surface includes an epoxy material in a range of 30% to 90%, by weight.

According to still further features in the described preferred embodiments, the metal working surface includes a steel working surface.

According to still further features in the described preferred embodiments, the mechanism is adapted such that the load on the contact surface is exerted in a substantially normal direction with respect to the contact surface and the working surface.

According to still further features in the described preferred embodiments, the particulate additive material has a Mohs hardness of less than 5.

According to still further features in the described preferred embodiments, the particulate additive material has a Mohs hardness of less than 3.

According to still further features in the described preferred embodiments, the lapping method further includes the step of: (d) applying microrelief to the metal working surface to produce at least one recess.

According to still further features in the described preferred embodiments, the particulate additive includes at least one material selected from the group consisting of cobalt chloride, molybdenum disulfide, graphite, a fullerene, tungsten disulfide, mica, boron nitride, silver sulfate, cadmium chloride, cadmium iodide, borax, boric acid and lead iodide.

According to still further features in the described preferred embodiments, the particulate matter is a filler material within the polymeric material.

According to still further features in the described preferred embodiments, at least 90% of the particulate matter have a diameter of less than 20 microns.

According to still further features in the described preferred embodiments, at least 90% of the particulate matter have a diameter of less than 10 microns.

According to still further features in the described preferred embodiments, at least 90% of the particulate matter have a diameter of less than 2 microns.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Throughout the drawings, like-referenced characters are used to designate like elements.

In the drawings:

FIG. 1A is a schematic description of the mechanically interacting surfaces having an interposed lubricating layer;

FIG. 1B is a schematic description of mechanically interacting surfaces having interacting asperities;

FIG. 1C(i)-(ii) schematically illustrate a working surface being conditioned in a conventional lapping process;

FIG. 2 is a description of a generalized concept of one aspect of the invention;

FIG. 3A is a schematic side view of a grooved cylinder in accordance with the invention;

FIG. 3B is a schematic view of a metal plate, the working surface of which is grooved, in accordance with the invention;

FIG. 4A is a pattern of dense sinusoidal grooving, in accordance with an embodiment of the invention;

FIG. 4B is a pattern of sinusoidal grooving, in accordance with an embodiment of the invention;

FIG. 4C is a sinusoidal pattern of grooving, containing overlapping waves, in accordance with an embodiment of the invention;

FIG. 4D is a pitted pattern of grooving in accordance with an embodiment of the invention;

FIG. 4E is a pattern of rhomboidal grooving, in accordance with an embodiment of the invention;

FIG. 4F is a pattern of helical grooving, in accordance with an embodiment of the invention;

FIG. 5 is a flow chart of the process of conditioning a working surface in accordance with one embodiment of the inventive lapping process;

FIG. 6A is schematic view of an interacting surface of the lapping technology disclosed herein;

FIG. 6B is a schematic description of a side view of the interacting surface of FIG. 6A;

FIG. 7A is a cross-sectional schematic description of a machined surface;

FIG. 7B is a cross-sectional schematic description of the surface after micro-grooving;

FIG. 7C is a cross-sectional schematic description of the grooved surface after undergoing the inventive lapping process;

FIG. 8A is a cross-sectional schematic description of the working surface, after micro-grooving, the micro-grooves being surrounded by bulges;

FIG. 8B is a cross-sectional schematic description of the surface of FIG. 8A, after undergoing the inventive lapping process;

FIG. 9A is a cross-sectional schematic description of a lapping tool—working surface interface prior to lapping, in accordance with the invention;

FIG. 9B is a cross-sectional schematic description of the lapping tool—working surface condition after lapping has progressed, in accordance with the invention;

FIG. 9C(i)-(iii) are an additional cross-sectional schematic representation of a working surface being conditioned in the inventive lapping process;

FIG. 10 is a schematic, cross-sectional view of a portion of a lapping tool having a polymeric layer containing a particulate additive material, according to the present invention;

FIG. 11 is a schematic, cross-sectional representation of a solid, organic layer deposited on a working surface, and having incorporated solid particles, according to the present invention;

FIG. 12 shows a portion of the representation of FIG. 12A, after removing several nanolayers of the working surface;

FIG. 13 is a schematic drawing of an exemplary tribological system according to one aspect of the present invention;

FIG. 14 is a cross-sectional schematic illustration showing a cross-sectional velocity profile of a fluid being transported in a conduit having an interior working surface according to the present invention;

FIG. 15 is a cross-sectional schematic illustration of an artificial joint for implanting in a living body;

FIG. 16 is an isometric schematic description of an experimental set-up for testing discs conditioned in accordance with the invention;

FIG. 17 is a schematic illustration of a test rig for evaluating the tribological properties of rollers processed in a “one drop” test;

FIG. 18 shows the friction coefficient at the stop point of the test, for each roller, and

FIG. 19 provides plots of the friction coefficient (μ) and wear (h) as a function of friction length (L).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a method and device for incorporating particulate additives into a metal work surface to produce a work surface having greatly improved tribological properties.

The principles and operation of the present invention may be better understood with reference to the drawings and the accompanying description.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawing. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

In accordance with the present invention, lubricated surfaces in relative sliding motion are treated to produce less wear and friction in the course of interaction. In most general terms, the process of the invention transforms a working surface so as to produce two interposed zones, one having a high degree of lubricant repellence, and the other having a relative attraction towards the lubricant. A schematic representation of the concept of the invention is shown in FIG. 2, to which reference is now made. A schematic working surface is shown which is composed of a combination of zones. The zones marked A are lubricant attractive and the zones marked R are relatively lubricant repelling.

In a preferred embodiment of the invention, the difference between the zones with respect to attraction to the lubricant is associated with a structural difference. The structural aspects of the system of this embodiment of the invention are schematically described in reference to FIGS. 3A-B. In FIG. 3A, a cylinder 50 has its surface structured such that one or more grooves, such as helical groove 52, are engraved on the surface. Typically, such grooves have a maximum depth of about 5-30 microns, and a width of about 100-1000 microns. The remainder of the original surface is one or more ridges, in this example, a helical ridge 54. Thus, the exterior of cylinder 50 includes two zones, the superficial zone that includes the ridges, and the recessed zone including the grooves. In FIG. 3B, a metal slab 60 has been processed in accordance with the present invention. The working surface, after undergoing a frictional interaction with another element (not shown), includes grooves 62, the assembly of which become the recessed zone, and alternate ridges 64, which form the superficial zone of the working surface of metal slab 60.

Zone Patterns

In FIGS. 4A-F are provided exemplary, schematic patterns of recesses, such as microgrooves, which are suitable for the structural aspects of embodiments of the present invention. FIGS. 4A-B show sinusoidal patterns of varying density; FIG. 4C shows a sinusoidal pattern containing overlapping sinuses; FIG. 4D shows a pitted pattern; FIG. 4E shows a pattern of rhomboids, and FIG. 4F shows a helical pattern. The diversity of optional patterns is very large, and the examples given above constitute only a representative handful.

Processing the Working Surface

In a preferred process for conditioning the working surface, described schematically in FIG. 5, the working surface is machined by abrading and/or lapping (step 90) so as to obtain a high degree of flatness and surface finish. In step 92, an optional recessed zone is formed, and in step 94, the superficial zone of the working surface is conditioned in a lapping step.

Lapping of the superficial zone has been found to achieve a very good flatness rating, and a very good finish. The lapping technique uses a free-flowing abrasive material, as compared to grinding, which uses fixed abrasives. Lapping is also well distinguished from polishing processes, which are characterized by high speeds and low loads, relative to lapping processes. The effect on the surface of the workpiece is very different. In lapping, the load and relative motion between the surface of the workpiece and the lapping tool surface cause the abrasive particles to cut stock out of the surface. In polishing, by sharp contrast, the relative motion between polishing tool and workpiece surface is of such high magnitude as to effect localized melting of the workpiece surface.

As used herein in the specification and in the claims section that follows, the term “lapping” is meant to exclude such polishing systems and methods.

FIG. 6A describes schematically an interacting surface 100, a working surface 102 for processing in accordance with an embodiment of the invention. A schematic sectional view of the surface is shown in FIG. 6B, indicating the position of an enlarged view of the cross-section shown in FIGS. 7A-C. In FIG. 7A, a machined surface 106 is shown. In FIG. 7B, surface 106 is shown after optional microgrooves or recessed microstructures 108 have been formed. In FIG. 7C, the working surface has been leveled and transformed by the inventive lapping process. A new plastically deformed region 110, which will be discussed in greater detail hereinbelow, has formed on the superficial zone.

The lapping step preferably succeeds the microgrooving step, because in forming the recessed microstructures on the surface, bulging of the surface around the microstructures is common. The bulges may appear even if the structural changes are effected by laser-cutting. This is illustrated schematically in FIGS. 8A-B, to which reference is now made. In FIG. 8A, recessed microstructures or microgrooves 121 have been formed in working surface 120. Around the edges of recessed microstructures 121 are disposed bulges 122, produced in the formation of microstructures 121. After the inventive lapping process, the bulges are leveled, and a plastically deformed region 124 is produced (see FIG. 8B) near the surface of working surface 120.

Lapping is the preferred mechanical finishing method for obtaining the characteristics of the working surface of the mechanical element in accordance with the present invention. The lapping is performed using a lapping tool, the surface of which is softer than the working surface of the processed mechanical part, and a paste containing abrasive grit. The paste may be a conventional paste used in conventional lapping processes. In order to be effective, the abrasive grit must be much harder than the face of the lapping tool, and harder than the processed working surface. Aluminum oxide has been found to be a suitable abrasive material for a variety of lapping surfaces and working surfaces, in accordance with the invention.

FIGS. 9A-B schematically present progressive steps in the inventive lapping process, in which the conditioning of the working surface is promoted. The initial condition of one aspect of the inventive lapping system 130 is shown schematically in FIG. 9A. The irregular topography of a working surface 132 (disposed on a workpiece 131) faces a lapping tool 134 and is separated by an irregular distance therefrom. Abrasive particles 136 are partially embedded in contact surface 135 of lapping tool 134, and to a lesser extent, in working surface 132. Working surface 132 and contact surface 135 are made to move in a relative motion by mechanism 138. This motion has an instantaneous magnitude V. Mechanism 138 also exerts a load, or a pressure PI, that is substantially normal to contact surface 135 and working surface 132.

In FIG. 9B, some lapping action has taken place, causing working surface 132 to become less irregular. As a result of the relative movement between the surfaces, the abrasive particles, such as abrasive particle 139, are now rounded to some extent, losing some of their sharp edges in the course of rubbing against the surfaces.

While initially, abrasive particles 136 penetrate into working surface 132 and gouge out material therefrom, as the process continues, and the abrasive particles become rounded, substantially no additional stock is removed from the processed part. Instead, the lapping movement effects a plastic deformation in working surface 132 of workpiece 131, so as to increase the micro-hardness of working surface 132.

FIG. 9C (i)-(iii) are an additional schematic representation of a working surface being conditioned in a lapping process and system of the present invention. In FIG. 9C(i), a working surface 132 of a workpiece 131 faces a contact surface 135 of lapping tool 134. An abrasive paste containing abrasive particles, of which is illustrated a typical abrasive particle 136, is disposed between working surface 132 and contact surface 135. As in conventional lapping technologies, contact surface 135 of lapping tool 134 is made of a material having a greater wear-resistance and a lower hardness with respect to working surface 132. The composition and size distribution of the abrasive particles are selected so as to readily wear down working surface 132 according to plan, such as reducing surface roughness to a particular or pre-determined roughness.

A load is exerted in a substantially normal direction to surfaces 132 and 135, causing abrasive particle 136 to penetrate working surface 132 and contact surface 135, and resulting in a pressure P being exerted on a section of abrasive particle 136 that is embedded in working surface 132. The penetration depth of abrasive particle 136 into working surface 132 is designated by h_(a2); the penetration depth of abrasive particle 136 into contact surface 135 is designated by h_(b2). Abrasive particle 136 penetrates into lapping tool 134 to a much greater extent than the penetration into workpiece 131, such that h_(b2)>>h_(a2). Significantly, because of the substantial elastic character of the deformation of inventive contact surface 135, the penetration depth of abrasive particle 136 into contact surface 135 is much larger than the penetration depths of identical abrasive particles into contact surfaces of the prior art (under the same pressure P), i.e.,

h_(b2)>h_(b1),

where h_(b1) is defined in FIG. 1C(i). Consequently, the penetration depth of abrasive particle 136 into working surface 132, ha, is much smaller than the corresponding penetration depth, h_(a1), of the prior art, i.e.,

h_(a2)<h_(a1).

In FIG. 9C(ii), workpiece 131 and lapping tool 134 are made to move in a relative velocity V. The pressure P, and relative velocity V of workpiece 131 and lapping tool 134, are of a magnitude such that abrasive particle 136, acting like a cutting tool, gouges out a chip of surface material from workpiece 131. This chip is typically much smaller than the chips that are gouged out of the working surfaces conditioned by lapping technologies of the prior art.

In FIGS. 9C(ii)-(iii), relative velocity V is selected such that a corresponding shear force Q is large enough, with respect to pressure P, such that the direction of combined force vector F on abrasive particle 136 causes abrasive particle 136 to rotate. During this rotation, the elasticity of lapping tool 134 and contact surface 135 results in less internal strains within abrasive particle 136, with respect to the prior art, such that a typical particle, such as abrasive particle 136, does not shatter, rather, the edges of the surface become rounded. An idealization of this rounding phenomenon is provided schematically in FIG. 9C(iii).

The working surfaces of the present invention have an intrinsic microstructure that influences various macroscopic properties of the surface. Without wishing to be limited by theory, it is believed that the inventive lapping system effects a plastic deformation in the working surface, so as to improve the microstructure of the working surface. One manifestation of the modified microstructure is a greatly increased micro-hardness.

The inventors have surprisingly discovered that the polymeric lapping tool surface, as exemplified hereinabove, can be filled with at least one material that enhances the performance of the surface of the workpiece during operation. Preferably, the surface-enhancing material is intimately mixed with the polymer material. The filler material is typically inert with respect to the polymer material.

Specifically, filler materials within the polymeric lapping tool surface can be transferred and incorporated into the surface of the workpiece during lapping, in order to obtain workpiece surfaces having tribologically-superior properties. Such filler materials include, but are not limited to, solid lubricants.

Solid lubricants, which include inorganic compounds, organic compounds, and metal in the form of films or particulate materials, provide barrier-layer type of lubrication for sliding surfaces. These materials are substantially solid at room temperature and above, but in some instances will be substantially liquids above room temperature.

The inorganic compounds include materials such as cobalt chloride, molybdenum disulfide, graphite, tungsten disulfide, mica, boron nitride, silver sulfate, cadmium chloride, cadmium iodide, borax, boric acid and lead iodide. These compounds exemplify the so-called layer-lattice solids in which strong covalent or ionic forces form bonds between atoms in an individual layer while weaker Van der Waals forces form bonds between the layers. They generally find use in high temperature applications because of their high melting points, high thermal stabilities in vacuum, low evaporation rates, and good radiation resistance. Especially suitable materials include formulated graphite and molybdenum disulfide. Both molybdenum disulfide and graphite have layer-lattice structures with strong bonding within the lattice and weak bonding between the layers. Sulfur-molybdenum-sulfur lattices form strong bonds whereas weak sulfur-sulfur bonds between the layers allow easy sliding of the layers over one another. Molybdenum disulfide and graphite are therefore especially important solid inorganic lubricants.

Fullerenes are suitable as particulate additive materials for incorporating within the polymeric lapping tool surface of the present invention.

Other suitable inorganic materials that do not have a layer-lattice structure include basic white lead or lead carbonate, zinc oxide, and lead monoxide.

Solid organic lubricant compounds include high melting organic powders such as phenanthrene, copper phthalocyanine, and mixtures with inorganic compounds and/or other lubricants. Copper phthalocyanine admixed with molybdenum disulfide is known to be a good roller bearing lubricant.

The solid particles listed above typically have a Mohs hardness of below 2.5 at room temperature. Many of the materials have a Mohs hardness of about 1 or less than 1.

The metal lubricants generally include soft metals such as gallium, indium, thallium, lead, tin, gold, silver, copper, rhodium, palladium, and platinum. The hardness of these materials tends to decrease substantially with increasing temperature.

Chalcogenides of the non-noble metals may also be employed, especially the oxides, selenides, or sulfides.

Conventional methods and conventional workpiece surfaces often require combining the solid lubricants with various binders that keep them in place on the moving workpiece surface. Binders are especially necessary in dry lubricant applications employing solid or particulate lubricants, and are sometimes described as bonded solid lubricants. Various thermosetting and thermoplastic and curable binder systems include phenolic, vinyl, acrylic, alkyd, polyurethane, silicone, and epoxy resins.

In the present invention, however, the solid lubricants are incorporated into the surface of the workpiece during the lapping machining procedure, such that binders are unnecessary. The inventive workpiece surfaces exhibit tribologically-superior properties with respect to prior-art workpiece surfaces having bound solid lubricants.

Moreover, in the inventive workpiece surface (and using the inventive lapping tool surface and method), the solid lubricants are incorporated in a firm and substantially permanent fashion. As used herein in the specification and in the claims section that follows, the term “incorporated”, “incorporation”, and the like, with respect to a particle and with respect to a working surface, refers to a particle that is so strongly attached to the working surface, that the particle remains attached thereto even after the working surface has been subjected to a cleaning process, as defined hereinbelow.

As used herein in the specification and in the claims section that follows, the term “cleaning”, “cleaned”, or “cleaning process”, with respect to a working surface, refers to the following procedure:

(step 1) immersion of the working surface in a bath filled with isopropanol or ethanol, and subjecting the immersed working surface to ultrasonic treatment for at least one minute;

(step 2) washing in ethanol followed by wiping the surface with a cloth soaked in ethanol, and

(step 3) subjection to a vacuum of at least 10⁻⁸ torr (and preferably 10⁻¹⁰ torr) for at least 5 minutes,

wherein the specific parameters of the ultrasonic treatment, the washing in ethanol, and the wiping are performed so as to remove loose particulate matter and organic debris, according to techniques that are known to one skilled in the art.

After lapping, the inventive working surface is subjected to such a rigorous cleaning process to remove loose particulate matter and organic debris.

Alternatively, the solid particles (e.g., solid lubricants) can be incorporated into the surface of the workpiece by using a polymeric lapping tool surface (such as those described herein) and adding these solid particles to the lapping system as free-flowing solid particles prior to effecting the lapping method. The free-flowing solid particles can be added to various abrasive pastes used in the lapping art, or added separately with respect to such abrasive pastes.

Typically, at least 90% of the incorporated solid particles have a diameter of less than 20 microns. Preferably, at least 90% of the incorporated solid particles have a diameter of less than 10 microns, more preferably, less than 5 microns, and most preferably, less than 2 microns.

An exemplary lapping tool surface of the present invention is synthesized as follows: an epoxy resin, a polyol and a di-isocyanate are reacted at a temperature exceeding room temperature and less than about 150° C. Subsequently, a hardener and solid lubricant particles are added and mixed in. As will be evident to one skilled in the art, the requisite curing conditions depend largely upon the particular qualities and ratios of the above-mentioned ingredients. It will be further evident to one skilled in the art that the polymer can be produced as a bulk polymer or as a molded polymer.

Advantageous ratios of the epoxy and polyurethane materials are provided hereinbelow.

However, it should be appreciated that other polymers or combinations of polymers having the requisite mechanical and physical properties for use in conjunction with the inventive device and method could be developed by one skilled in the art.

Mechanical Criteria for the Contact Surface of the Lapping Tool

It has been found that lapping using a lapping tool having a somewhat elastic, organic, polymeric surface promotes micro-hardness and other tribological properties of the working surface. The mechanical criteria with which the inventive polymeric surface should preferably comply include:

-   -   1. wear resistance with respect to the abrasive paste used in         the lapping process;     -   2. elastic deformation such that individual abrasive particles         protrude into, and are held by, the polymeric surface; as the         individual abrasive particles rotate during contact with the         working surface, the elastic deformation should enable the         particles to be absorbed into the polymeric surface in varying         depths, according to the varying pressures exerted between the         particles and the working surface. Consequently, the abrasive         particles rotate against the working surface and become more         rounded with time, instead of undergoing comminution (being         ground into a fine powder);     -   3. the hardness of the polymeric surface should be selected such         that the elastic layer does not appreciably break or grind the         abrasive powder. Thus, contact surface 135 of lapping tool 134         (see FIGS. 9A-9B, and FIGS. 9C(i)-9C(iii)) is an organic,         polymeric surface. If contact surface 135 is a layer that is         mechanically supported (e.g., on a metal backing), surface 135         preferably has a thickness T (see FIG. 9B) of at least 0.5 mm.         Alternatively, organic, polymeric contact surface 135 has a         thickness T of at least 5 mm and more preferably at least 8-10         mm, such that contact surface 135 is substantially         self-supporting.

The inventors have further discovered that a mixture of epoxy cement and polyurethane in a ratio of about 25:75 to 90:10, by weight, is suitable for forming the contact surface of the lapping tool. In the epoxy cement/polyurethane mixture, the epoxy provides the hardness, whereas the polyurethane provides the requisite elasticity and wear-resistance. It is believed that the polyurethane also contributes more significantly to the deposition of an organic, possibly polymeric nanolayer on at least a portion of the working surface, as will be developed in further detail hereinbelow. It will be appreciated by one skilled in the art that the production of the epoxy cement/polyurethane mixture can be achieved using known synthesis and production techniques.

More preferably, the weight ratio of epoxy cement to polyurethane ranges from about 1:2 to about 2:1, and even more preferably, from about 3:5 to about 7:5.

In terms of absolute composition, by weight, the lapping tool surface typically contains at least 10% polyurethane, preferably, between 20% and 75% polyurethane, more preferably, between 40% and 75% polyurethane, and most preferably, between 40% (inclusive) and 65% (inclusive).

The inventive contact surface of the lapping tool should preferably contain, by weight, at least 10% epoxy, more preferably, at least 35% epoxy, yet more preferably, at least 40% epoxy, and most preferably, between 40% (inclusive) and 70% (inclusive). In some applications, however, the elastic layer should preferably contain, by weight, at least 60% epoxy, and in some cases, at least 80% epoxy.

Preferably, the inventive contact surface (lapping surface) should have the following combination of physical and mechanical properties:

-   -   Shore D hardness within a range of 40-90, preferably 60-90, more         preferably 65-82, and most preferably, 70-80;     -   impact resistance (with notch) within a range of 3-20 kJ/m²,         preferably 3-12 kJ/m², more preferably 4-9 kJ/m², and most         preferably, 5-8 kJ/m², according to ASTM STANDARD D 256-97;         It should be appreciated that a variety of materials or         combinations of materials could be developed, by one skilled in         the art, that would satisfy these physical and mechanical         property requirements.

FIG. 10 is a schematic, cross-sectional view of a portion of an inventive lapping tool 600 having a base 610 and a polymeric layer 620 attached thereto. Polymeric layer 620 forms the contact surface in the lapping tool and process described hereinabove (see FIGS. 9A-C). Within polymeric layer 620 is dispersed a large plurality of solid particles 630. Presently preferred materials for solid particles 630 are soft solid lubricant particles such as molybdenum disulfide, graphite, and fullerenes.

With reference now to FIG. 11, using the lapping tool and method of the present invention, it has been discovered that an extremely-thin, typically nanometric, solid, organic layer 420 is applied on a working surface 410. A substantial (though not necessarily exclusive) source of the organic layer is the organic material on the surface of the inventive lapping tool. Alternatively or additionally, the source of the organic layer can be organic particles and materials (e.g., polymeric materials) added to the abrasive paste used in the lapping process.

In the representation provided in FIG. 11, solid particles 630 are firmly incorporated in working surface 410.

Typically, asperities 412,414, which protrude from working surface 410, are also covered by coating 420. In FIG. 12, which shows a portion of working surface 410 from FIG. 11, layer 420 exhibits wear, particularly in the area covering the asperities. Eventually, the asperities themselves, such as asperity 414, undergo attrition. In this state, an exposed surface area 416 of asperity 414 is largely surrounded by exposed area 422. Consequently, any lubricant in the vicinity of exposed surface area 416 tends to migrate from exposed area 422 towards exposed surface area 416 of asperity 414, such that superior lubricating conditions are maintained.

It must be emphasized that the working surface of FIG. 11 differs from coated working surfaces of the prior art in various fundamental ways. These include:

-   -   the layer in FIG. 11 is a nanometric layer having an average         thickness of up to 200 nm, and more preferably, 5-200 nm.         Typically, the nanometric layer has an average thickness of         5-100 nm. Excellent experimental results have been obtained for         working surfaces having nanometric layers of an average         thickness of 5-50 nm.     -   the deposition of the nanometric layer is performed by the         inventive lapping method itself.     -   the material source of the nanometric layer is from the         inventive contact surface of the lapping tool, or from materials         disposed in the paste.     -   incorporated in the layer are a large plurality of soft solid         particles such as known solid lubricant materials.     -   the nanometric layer is intimately bonded to the working surface         by filling the nanometric contours of the working surface.     -   the nanometric layer is strongly adhesive to the working         surface. Consequently, the layer is not subject to the phenomena         of peeling, flaking, crumbling, etc., which characterize         coatings of the prior art.     -   the microrelief is performed prior to deposition of the         nanometric coating.

It must be further emphasized that the nanometric film is bonded, on one side, to the surface of the workpiece, and on the opposite side, the nanometric film becomes the working surface of the workpiece, being exposed to the lubricant and to the frictional forces resulting from the relative motion of the working and counter surfaces (and the load thereon).

FIG. 13 is a schematic drawing of an exemplary tribological system 500 according to one aspect of the present invention. Tribological system 500 includes a rotating working piece 502 (mechanism of rotation, not shown, is standard), having a working surface (contact area) 503 bearing a load L, a counter surface disposed within stationary element (bushing) 504, and a lubricant (not shown) disposed between working surface 502 and counter surface 504. Working surface 503 is an inventive working surface of the present invention, as described hereinabove. Recessed zones (grooves 506) serve as a reservoir for the lubricant and as a trap for debris.

It must be emphasized that the inventive lapping method and inventive working surface produced thereby, after producing grooving patterns in the working surface, achieves a surprisingly-high performance with respect to prior-art lapping surfaces combined with the identical grooving patterns, and as demonstrated experimentally (see Example 3 and Table 4 below).

In another embodiment of the present invention, the inventive work surface is utilized in the internal wall of a surface of a vessel or conduit used for the transport of fluids, so as to reduce the friction at the surface of the internal walls, and correspondingly reduce the pressure loss and energy cost of pumping the fluid.

As used herein in the specification and in the claims section that follows, the term “conduit” refers to a vessel used for the transport of at least one liquid. The term “conduit” is specifically meant to include a tube, pipe, open conduit, internal surface of a pump, etc.).

FIG. 14 is a schematic diagram showing a cross-sectional velocity profile 180 of a fluid being transported in a conduit 182. Without wishing to be limited by theory, it is believed that due to the unique surface structure and energy of the inventive work surface, the forces of adherence adjacent to an inner working surface 183 of wall 184 are appreciably reduced. It is further believed that the thickness of the boundary layer adjacent to inner working surface 183 is also appreciably reduced, such that bulk-phase flow occurs much closer to wall 184 than in conventional metal conduits.

In another embodiment of the present invention, the inventive work surface and inventive lapping method and device are utilized in the production of artificial joints, e.g., hip joints. Conventional hip joints suffer from a number of disadvantages, which tend to reduce their effectiveness during use, and also shorten their life span. First, since the synovial fluid produced by the body after a joint replacement operation is considerably more diluted and thus 80% less viscous than the synovial fluid originally present, the artificial joint components are never completely separated from each other by a fluid film. The materials used for artificial joints, as well as the sliding-regime parameters, allow only two types of lubrication: (i) mixed lubrication, and (ii) boundary lubrication, such that the load is carried by the metal femoral head surface sliding on the plastic or metal acetabular socket surface. This results in accelerated wear of the components, increasing the frictional forces, and contributes to the loosening of the joint components and, ultimately, to the malfunction of the joint.

The high wear rate of the ultra-high-weight polyethylene (UHWPE) cup results in increased penetration of the metal head into the cup, leading to abnormal biomechanics, which can cause loosening of the cup. Furthermore, polyethylene debris, which is generated during the wearing of the cup, produces adverse tissue reaction, which can induce the loosening of both prosthetic components, as well as cause other complications. Increased wear also produces metal wear particles, which penetrate tissues in the vicinity of the prosthesis. In addition, fibrous capsules, formed mainly of collagen, frequently surround the metallic and plastic wear particles. Wear of the metal components also produces metal ions, which are transported, with other particles, from the implanted prosthesis to various internal organs of the patient. These phenomena adversely affect the use of the prosthesis.

In addition, bone and bone cement particles, which remain in the cup during surgery, or which enter the contact zone between the hip and the cup during articulation, tend to become embedded in the cup surface. These embedded bone particles can cause damage to the head, which can, in turn, bring about greatly increased wear of the cup.

The treatment of the head friction surface using microstructuring technology, so as to reduce the wear of the friction surfaces, has been suggested in the literature (see Levitin, M., and Shamshidov, B., “A Laboratory Study of Friction in Hip Implants”, Tribotest Journal 5-4, June 1999, the contents of which are incorporated by reference for all purposes as if fully set forth herein). The microrelief technology improves lubrication and friction characteristics, and facilitates the removal of wear debris, bone fractions, and bone cement particles from the friction zone between the male and female components of the joint.

There is, however, a well-recognized need for further improvement in reducing friction and wear in artificial joints. In another embodiment of the present invention, shown in FIG. 15, a metal joint head 441 is engaged within a metal cup 442. Optionally, metal joint head 441 has grooves 444 (recesses, pores, etc.) according to microstructuring technology known in the art. Metal joint head 441 has been subjected to the lapping methods of the present invention, so as to produce the inventive working surface.

There is, however, a well recognized need for further improvement in reducing friction and wear in artificial joints. In another embodiment of the present invention, shown in FIG. 15, a metal joint head 441 is engaged within a metal cup 442. Optionally, metal joint head 441 has grooves 444 (recesses, pores, etc.) according to microstructuring technologies known in the art. Metal joint head 441 has been subjected to the lapping methods of the present invention, so as to produce the inventive working surface. Preferably, a working surface 443 of metal joint head 441 is at least partially covered with an organic layer. It is also preferable to have solid lubricant particles incorporated into working surface 443, as described hereinabove with reference to FIG. 11.

EXAMPLES

Reference is now made to the following examples, which together with the above description, illustrate the invention in a non-limiting fashion.

Example 1

The experimental set-up is described schematically in FIG. 16, to which reference is now made. An interchangeable set of carbon steel discs of 30 mm diameter, such as disc 186, rotatable around an axle, is made to rotate against a flat counter-plate 192 for measuring wear. The discs are made of carbon steel grade 1045, having an HRC of 27-30. Electrical motor or gear 190 supplies the torque for the rotation. Counter-plate 192 is made of a copper alloy (UNS C93700 (HRC=22-24)), ground to an average roughness (Ra) of 0.4 micrometers. Counter-plate 192 has a support 194, which has an adjustable height for controlling the force applied on disc 186.

The control discs have a conventional grinding finish (Ra=0.4 micrometers), whereas the test discs undergo further treatment by micro-grooving face 196 of the disc, and then by lapping, in accordance with the present invention. During the experiments, a permanent load of a 100 N is applied to the disc in the direction of the counter plate 192. One drop of Amoco Industrial Oil 32 (equivalent to ASTM 150 Turbine Oil) is applied to the dry friction surface before activating the motor to achieve a constant rotation rate of 250 rpm. The time to seizure, which is the accumulated time from start of turning, until the time in which movement was stopped by seizure, was measured.

After 16-18 minutes, all control discs underwent seizure. By sharp contrast, the disc that was treated by micro-grooving and lapping, according to the present invention, continued to revolve without stopping, for a period above 40 hours, at which point the experiment was curtailed. Seizure of the treated disc did not occur.

In another experiment, the disc was rotated at 180 rpm. A group of control discs was subjected to finishing by grinding. A second group of discs was subjected to micro-grooving. A third group of discs was subjected to micro-grooving and to lapping, according to the present invention. The results of a one-drop test are provided in Table 2. The path of the disc until seizure, the coefficient of friction, and the intensity of wear (measured by peak depression formed on the counter-plate as a result of the friction with the disc) were calculated.

TABLE 2 Results of Discs Rolling Against a Counter-Plate Surface Calculated path treatment of until seizure (in Coefficient of Intensity of wear disc Km) friction (in mm³/Km). Grinding 1.5 0.1-0.2 0.2 Grinding + 8.7 0.08-0.12 0.02 micro-grooving Grinding + At least 29.7 0.03-0.04 0.001 micro-grooving + lapping

The inventive working surface of the present invention, incorporated in various mechanical elements that engaged in frictional forces, reduces friction and wear, risk of seizure, and prolongs the operating life of such elements. In punching applications, the qualities of the working surface are improved, and a power reduction of up to 30% is observed.

In internal combustion engines, the inventive working surface, and the inventive system for production thereof, were applied to 120 mm cylinder sleeves of diesel engines and to 108 mm diameter motorcycle engines. The results of the tests demonstrate that for a given performance level, the use of sleeves having the inventive work surfaces, as compared with conventional sleeves, reduces fuel consumption. In addition, the sleeves having the inventive working surfaces have a characteristically longer lifetime, and lose less oil.

Example 2

A roller on block tribo-tester was used to evaluate the tribological properties of rollers processed according to the present invention, in a “one drop test”. The test rig is described schematically in FIG. 17. A rotating roller 2 is brought into contact with a stationary block 3 under a given load P while a very small amount of lubricant (one drop) is applied to the contact. A force transducer 4 is used to measure the friction force F and a proximity probe 9 measures the variation in the gap, thus providing the total wear of roller 2 and block 3. Both friction and wear are continuously monitored and recorded as functions of time. The test is stopped at the occurrence of any one of the following three events: (a) the friction coefficient=F/P reaches a value of 0.3; (b) seizure starts between the roller and the block (characterized by a sudden, sharp increase in friction and corresponding increase in noise level), or (c) the friction reaches a maximum value and starts decreasing. The test duration is defined as the time elapsed from the start of the test until the end of the test due to the occurrence of events (a) or (b) described above, or the time corresponding to the maximum friction in case of event (c). It should be noted that in this special case (c), the test is continued for about 20 minutes beyond the “test duration” prior to complete stop. For each new test, block 3 is moved horizontally in its holder 6 to provide a fresh contact.

Tests were performed on each of 6 steel roller specimens, using a bronze block as the counter-surface. Roller #1 and roller #6 are reference rollers, as described in Table 3 hereinbelow. Rollers #2-5 were processed with combined microrelief, according to the present invention, with various groove patterns and groove areas. SAE 40 oil at room temperature was used as the lubricant. One drop of oil was placed on roller 2, which is then brought into light contact (18 N load) with bronze block 3 and turned (manually) two revolutions to spread the oil over the entire circumference. The amount of excess oil transferred to the block was wiped off with a clean paper towel, leaving only the roller lubricated. The load was increased to a level of P=150 N, and the test was started with a roller speed of 105±5 rpm.

Table 2 presents the test duration, in minutes, of each roller, and indicates the type of event that caused the stop of the test. FIG. 18 shows the friction coefficient at the stop point of the test for each roller.

Reference roller #1 seized after a very short time of 6 minutes at a friction coefficient=0.23. Roller #6 exhibited a continuously increasing friction, and the test was stopped after 21 minutes, at a friction coefficient=0.3 and seizure inception. All rollers processed in accordance with the present invention (rollers #2 to #5) showed an increased friction up to a certain maximum value, followed by a decrease in the friction. The maximum friction coefficient in these 4 rollers was no more than 0.18. Roller #5 had a friction coefficient of 0.11, which was the lowest friction coefficient of the six rollers.

A graph of the friction coefficient (μ) and wear (h) as a function of friction length (L) is provided in FIG. 19.

TABLE 3 Roller # 1 6 (reference) 2 3 4 5 (reference) Roller SAE 4340 SAE 4340 SAE 4340 SAE 4340 SAE 4340 SAE 4340 Material steel steel steel steel steel steel Roller Prep. ground inventive inventive inventive inventive regular microrelief surface CMR CMR CMR CMR without bulges Heat Ra ≈ 0.2μ Ra ≈ 0.2μ Ra ≈ 0.2μ Ra ≈ 0.2μ Ra ≈ 0.2μ Ra ≈ 0.2μ Treatment HRC 52-54 HRC 52-54 HRC 52-54 HRC 52-54 HRC 52-54 HRC 52-54 Test 6 52 53 25 37 21 duration (min) Stop event B C C C C A & B

Example 3

A roller on block tribo-tester was used to evaluate the tribological properties of rollers in a “one drop test”. Sliding distance tests were performed on each of four hardened-steel roller specimens, using a hardened-steel block as the counter-surface.

Roller specimen I was prepared using a conventional lapping method;

roller specimen II was prepared using a lapping method of the present invention;

roller specimen III was prepared by grooving followed by the conventional lapping method used in preparing roller specimen I, and

roller specimen IV was prepared by grooving followed by the inventive lapping method used in preparing roller specimen II.

The results of the sliding tests are presented in Table 4. Roller specimen II, prepared using a lapping method of the present invention, achieved a sliding distance of 1373 meters, nearly double that of reference roller specimen I, which was prepared using a conventional lapping method. Roller specimen IV, prepared by grooving followed by the lapping method used in preparing roller specimen II, achieved a sliding distance of 9060 meters, more than a fourfold increase in sliding distance with respect to that of reference roller specimen III, which was prepared by grooving followed by using the conventional lapping method used in preparing roller specimen I.

TABLE 4 Specimen Sliding Distance (meters) roller specimen I 709 roller specimen II 1373 roller specimen III 2061 roller specimen IV 9060

Example 4

A roller on block tribo-tester was used to evaluate the tribological properties of rollers in a “one drop test”. Sliding distance tests were performed on four identical, hardened-steel roller specimens, using a hardened-steel block as the counter-surface.

The surface of roller specimen I was not subjected to lapping.

The surface of roller specimen II was subjected to lapping using cast iron, a conventional lapping material.

The surface of roller specimen III was subjected to lapping using a lapping surface made of epoxy/polyurethane.

The surface of roller specimen IV was subjected to lapping using a lapping surface made of epoxy/polyurethane and containing particles of molybdenum sulfide (from Acros Organics®, New Jersey, USA), according to the present invention. The molybdenum sulfide is a dark gray powder, −325 mesh.

Friction test conditions: One-drop test; roller-on-block, both steel SAE 4340, Hardness Rockwell C (HRc) 52-54; radial force 400N; linear speed 0.65 m/sec; lubricant SN-90 (basic neutral oil).

The results of the sliding tests are presented in Table 5. Roller specimens I and II, prepared without lapping and with conventional lapping, respectively, achieved sliding distances that are well below 1000 meters. Roller specimen III, prepared with a lapping surface made of epoxy/polyurethane polymer according to the FRICSO® technology, achieved a sliding distance of about 5000 meters.

TABLE 5 Specimen No. I II III IV Lapping materials Testing No lapping Cast Epoxy/poly- Inventive parameters: Iron urethane Polymer with polymer MoS₂ Sliding distance 400 600 5,100 30,000 (m) Friction 0.15 0.11 0.05 0.04 coefficient

Surprisingly, roller specimen IV, prepared with a lapping surface made of the identical epoxy/polyurethane polymer of specimen III, but containing molybdenum sulfide particles, incorporated using the lapping method and device of the instant invention, achieved a sliding distance of about 30,000 meters, about 6 times the sliding distance attained by specimen III, and at least 40 times the sliding distance attained by specimens I and II.

The friction coefficient of roller specimen IV is lower than that of specimen III and significantly lower than the friction coefficients of specimens I and II.

As used herein in the specification and in the claims section that follows, the term “impact resistance” refers to the impact resistance, with notch, in units of kJ/m², as determined by ASTM STANDARD D 256-97.

The hardness testing of plastics and hard rubbers is most commonly measured by the Shore D test, with higher numbers signifying greater resistance.

As used herein in the specification and in the claims section that follows, the term “Shore D hardness”, and the like, refers to a measure of the resistance of material to indentation, according to the standard ASTM test (D 2240-97).

As used herein in the specification and in the claims section that follows, the term “freely disposed”, regarding abrasive particles, relates to the free-flowing state of abrasive particles as in typical lapping methods of the prior art.

As used herein in the specification and in the claims section that follows, the term “intimately bonded”, with respect to a film or layer and a working surface, refers to a nanometric, adhesive film having a contour that complements the micro-contour of the working surface, such that the film or layer is firmly attached to the working surface along the entire contour thereof.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication was specifically and individually indicated to be incorporated herein by reference. 

1. A mechanical device for lapping a metal working surface, the device comprising: (a) a workpiece having the metal working surface; (b) a contact surface, disposed generally opposite said working surface, said contact surface for moving in a relative motion to said working surface; (c) a plurality of abrasive particles, said particles disposed between said contact surface and said working surface, and (d) a mechanism, associated with at least one of said working surface and said contact surface, for applying said relative motion, and for exerting a load on said contact surface and said working surface, said contact surface for providing an at least partially elastic interaction with said plurality of abrasive particles, wherein, associated with said contact surface is a particulate additive material, and wherein, upon activation of said mechanism, said load causes a portion of said abrasive particles to contact said working surface, and wherein said relative motion under said load effects incorporation of a portion of said particulate additive material into said metal working surface.
 2. The mechanical device of claim 1, wherein said contact surface has a Shore D hardness within a range of 40-90.
 3. The mechanical device of claim 1, wherein said particulate additive material includes a solid lubricant.
 4. The mechanical device of claim 1, wherein said abrasive particles are freely disposed between said contact surface and said working surface.
 5. The mechanical device of claim 1, wherein said particulate additive material is disposed within said contact surface, such that upon said activation of said mechanism, said relative motion causes at least a portion of said particulate additive material to be mechanically transferred from said contact surface and to effect said incorporation of said particulate additive material into said metal working surface.
 6. The mechanical device of claim 1, wherein said contact surface includes a polymeric material, and wherein said particulate additive material is intimately dispersed within said polymeric material.
 7. The mechanical device of claim 6, wherein said polymeric material includes an epoxy material.
 8. The mechanical device of claim 6, wherein said particulate additive material includes a solid lubricant.
 9. The mechanical device of claim 5, wherein said particulate additive material includes a solid lubricant.
 10. The mechanical device of claim 5, wherein said Shore D hardness is within a range of 65-85.
 11. The mechanical device of claim 5, wherein said Shore D hardness is within a range of 65-90, and wherein said impact resistance is within a range of 4-12 kJ/m².
 12. The mechanical device of claim 5, wherein said Shore D hardness is within a range of 70-80, and wherein said impact resistance is within a range of 5-8 kJ/m².
 13. The mechanical device of claim 1, wherein said contact surface is disposed on a lapping tool.
 14. The mechanical device of claim 1, wherein said abrasive particles include alumina particles.
 15. The mechanical device of claim 1, wherein a composition of said contact surface includes both an epoxy material and polyurethane, and wherein said Shore D hardness is within a range of 65-90, and said impact resistance is within a range of 4-9 kJ/m².
 16. The mechanical device of claim 1, wherein a composition of said contact surface includes an epoxy material and polyurethane in a weight ratio of 25:75 to 90:10.
 17. The mechanical device of claim 1, wherein a composition of said contact surface includes polyurethane in a range of 3% to 75%, by weight.
 18. The mechanical device of claim 1, wherein a composition of said contact surface includes an epoxy material in a range of 30% to 90%, by weight.
 19. The mechanical device of claim 1, wherein said metal working surface includes a steel working surface.
 20. The mechanical device of claim 1, wherein said mechanism is adapted such that said load on said contact surface is exerted in a substantially normal direction with respect to said contact surface and said working surface.
 21. The mechanical device of claim 1, wherein said particulate additive material has a Mohs hardness of less than
 5. 22. The mechanical device of claim 1, wherein said particulate additive material has a Mohs hardness of less than
 3. 23. A lapping method comprising the steps of: (a) providing a system including: (i) a metal workpiece having a metal working surface; (ii) a contact surface, disposed generally opposite said working surface, said contact surface for moving in a relative motion to said working surface; (iii) a plurality of abrasive particles, said particles disposed between said contact surface and said working surface, and (iv) a plurality of solid particles, associated with said contact surface; (b) exerting a load in a substantially normal direction to said contact surface and said metal working surface, (c) lapping said workpiece by applying a relative motion between said metal working surface and said contact surface, so as to (i) effect an at least partially elastic interaction between said contact surface and said abrasive particles such that at least a portion of said abrasive particles penetrate both said working surface and said contact surface, and (ii) incorporate said particulate additive into said metal working surface.
 24. The lapping method of claim 23, further comprising the step of: (d) applying microrelief to said metal working surface to produce at least one recess.
 25. The lapping method of claim 24, wherein said particulate additive includes at least one material selected from the group consisting of cobalt chloride, molybdenum disulfide, graphite, a fullerene, tungsten disulfide, mica, boron nitride, silver sulfate, cadmium chloride, cadmium iodide, borax, boric acid and lead iodide.
 26. A mechanical device for lapping a metal working surface of a workpiece, the device comprising: a contact surface, for disposing generally opposite the metal working surface, said contact surface for moving in a relative motion to the working surface, said contact surface including: (a) at least one polymeric material, and (b) particulate matter, dispersed within said polymeric material, said contact surface having a Shore D hardness within a range of 65-90, said contact surface designed and configured such that during the lapping of the metal working surface of the workpiece, said particulate matter is mechanically transferred from said contact surface and incorporated into said metal working surface.
 27. The mechanical device of claim 26, wherein said particulate matter includes a solid lubricant.
 28. The mechanical device of claim 26, wherein said polymeric material includes an epoxy material.
 29. The mechanical device of claim 26, wherein said polymeric material includes a polyurethane.
 30. The mechanical device of claim 26, wherein said particulate matter is a filler material within said polymeric material.
 31. The mechanical device of claim 26, wherein said particulate matter has a Mohs hardness of less than
 5. 32. The mechanical device of claim 26, wherein said particulate matter has a Mohs hardness of less than
 3. 33. The mechanical device of claim 26, wherein at least 90% of said particulate matter have a diameter of less than 20 microns.
 34. The mechanical device of claim 26, wherein at least 90% of said particulate matter have a diameter of less than 10 microns.
 35. The mechanical device of claim 26, wherein at least 90% of said particulate matter have a diameter of less than 2 microns. 